ANSAN, South Korea / SEOUL - A floral tribute to the children who drowned in a sinking South Korean ferry features photographs of the victims in their school uniforms, while lines of empty spaces wait to be filled with photos once those still missing are confirmed dead.

The pictures, flowers and spaces are banked up the entire wall of a gymnasium near Danwon High School in Ansan, on the outskirts of Seoul.

"There are too many pictures, way more than I thought," said crying university student Jung Sun-a, 24. "And they are too young in these pictures. I really hope they can fulfil their dream in the next life. And I hope the missing kids will also come back to their parents as soon as possible."

One wailing old woman shouted out for her granddaughter, Lee Bomi.

"Bomi is still in darkness. She hasn't come home yet. What are we going to do? I came here to ask you. She is still in dark waters. What am I supposed to do?"

The Sewol ferry, weighing almost 7,000 tons, sank on a routine trip from the port of Incheon, near Seoul, to the southern holiday island of Jeju. Investigations are focused on human error and mechanical failure.

More than 300 people, most of them students and teachers from Danwon High School have died or are missing and presumed dead after the April 16 disaster.

The confirmed death toll on Friday was 181.

School classes resumed on Thursday in sombre mood. In the classrooms of the missing, friends posted messages on desks, blackboards and windows, in the days after disaster struck, asking for the safe return of their friends.

One note was stuck to the window of an empty classroom in the days when hopes for finding the passengers alive were fading fast. It was addressed to a girl called Si-yeon.

"Si-yeon, It's me, your oppa (male friend). I miss you a lot. I am so worried. Please come out of that ferry. We ought to go and eat your favourite things, sweet potatoes, cheese and tangerines," it read.

"It must be really cold in there. I am so sorry that I cannot do anything for you. It makes me feel so frustrated - there is nothing else I can do but pray for you. I don't even want to imagine how scared you must be. I hope you are alive. I won't give up, I will wait for you. I want to tell you that I love you."

A professor who led a psychological counselling at the school said the children now distrusted adults who fought amongst themselves, did little to rescue the passengers and told them to stay put.

"That is an obstacle in our treatment," he told local radio. "Without dealing with the mistrust, it is hard to approach them to help cure them. Yet such distrust cannot be dealt with words only. Once betrayed, how do you expect them to believe us again?"

CREW MEMBERS ARRESTED

Captain Lee Joon-seok, 69, and other crew members who abandoned ship after telling the children to stay put in their cabins have been arrested on negligence charges. Lee was also charged with undertaking an "excessive change of course without slowing down".

One crew member said after a brief appearance in court on Thursday she and six colleagues had been "under command" to abandon ship. Another was asked if there was any discussion about trying to save the children.

"At that moment, we were on the third floor and except for the third floor situation, we weren't aware of anything else," the crew member said.

Prosecutors have raided the home of Yoo Byung-un, the head of a family that owns the Chonghaejin Marine Co. Ltd, the company that operated the Sewol. They seized another ferry run by the company and found that life rafts and escape chutes were not working properly.

"I'm not saying it automatically means Sewol's safety equipment was faulty, but it helps to deduce the state of maintenance," one investigator told Reuters.

Prosecutors said on Friday they had told Yoo's younger son, who is staying in New York, and daughter to return by Tuesday for investigation.

Along with his elder brother, Yoo Hyuk-kee, Yoo is the biggest shareholder of a holding company that owns Chonghaejin Marine and its other affiliates.

Prosecutors said they had found some data have been deleted from computers they confiscated in the raids and some computers had been replaced.

The Sewol, 146 metres (479 ft) long and 22 metres wide, was more than three times overloaded, according to official recommendations, with cargo poorly stowed and inadequate ballast.

Moon Ki-han, an executive at Uryeon (Union Transport Co.), the firm that supervised cargo loading, told Reuters there were 105 containers onboard, some of which toppled into the sea as the ship listed.

Forty-five were loaded on to the front deck and 60 into the lower decks, Moon said. In total, the ship was carrying 3,600 metric tons of cargo including containers, vehicles and other goods, he said.

A member of parliament this week said the Korean Register of Shipping recommended a load of 987 tons for the Sewol.

(Additional reporting by Jack Kim in Mokpo and Kim Miyoung and Cho Meeyoung in Seoul; Writing by Nick Macfie; Editing by Simon Cameron-Moore)